$OpenBSD: patch-util_c,v 1.1 2017/06/09 13:32:29 sthen Exp $

Index: util.c
--- util.c.orig
+++ util.c
@@ -172,6 +172,10 @@ void *mem_chunk(off_t base, size_t len, const char *de
 	if ((fd = open(devmem, O_RDONLY)) == -1)
 	{
 		perror(devmem);
+		if (errno == EPERM) {
+			fprintf(stderr, "Note: requires running as root with "
+			    "access to kernel memory (kern.allowkmem=1).\n");
+		}
 		return NULL;
 	}
 
